After spending more than $450,000 this week to win one House race and lose another in Ohio, a Texas-based super PAC that claims to be taking nonpartisan aim at congressional incumbents is now dropping a money bomb on embattled Alabama Rep. Spencer Bachus.

In the last 48 hours, the Campaign for Primary Accountability (CPA) has filed reports for $153,267 in independent expenditures, almost all in Alabama. The group is spending to defeat two veteran members of Congress: five-term Rep. Jo Bonner and ten-term Rep. Spencer Bachus in the Tuesday primary. Most of CPA's spending takes aim at Bachus, who chairs the House Financial Services Committee and is reportedly under investigation for insider trading. CPA this week unveiled a new TV ad against him.

The spending spree puts total spending for CPA, already one of the top 20 super PACs on Sunlight's tracker, at $572,316.

The group describes its primary mission as targeting incumbents, but its biggest investment so far has been in a race where it choose between two longtime members of the House of Representatives.

Schmidt was defeated by a Tea Party-backed challenger, but the ideological motivation in CPA's other Ohio investment is harder to divine. A comparison of voting records using Sunlight's Open Congress tool reveals little difference between Democrats Kucinich and Kaptur, who were drawn into the same district by the legislature, which had to eliminate two seats in the once-a-decade congressional reapportionment following the U.S. Census.

CPA, which popped up late last year and had raised over $1.8 million by the end of January, also benefits from ties to the Alliance for Self-Governance, a nonprofit focused on get-out-the-vote efforts. Though CPA spokesman Curtis Ellis maintained that the two organizations are not officially connected, he acknowledged that both are active in many of the same districts, both are underwritten by many of the same people and both were founded by the same two men. Like the CPA, the Alliance for Self-Governance is focused on primary elections, according to the nonprofit’s website. For instance, the nonprofit is working to increase voter turnout in Chicago, Ellis said, just as the super PAC targets Jesse Jackson, Jr., D-Ill., whom Ellis called “Mr. Insider.” In the March 20 Democratic primary, the CPA Is backing Debbie Halvorson, who, although not an incumbent, did serve one term in the last Congress. She is in an increasingly bitter race that Jackson is trying to win in a district substantially altered by the new lines drawn to conform to the 2010 Census.

As of the end of January, the CPA was the 16th-biggest super PAC in the nation based on its contributions at the time — a number Curtis declined to update. Although the two founders claimed in a press release that the super PAC spent $200,000 in Schmidt’s race, it has only disclosed about $50,000 in spending against her to the Federal Election Commission (FEC).

When asked about the discrepancy, Ellis said it could be due to either last-minute spending or the spending by the nonprofit Alliance for Self-Governance — spending that must be nonpartisan if it is not reported to the FEC.

CPA is currently targeting 11 incumbents — five Democrats and six Republicans — in early primaries but plans to take aim at more.

In all but one of the six races where CPA has spent so far, it’s the only super PAC in the game. Super PACs can raise an unlimited amount of money for independent expenditures to back or oppose candidates. Here are the incumbents the CPA is targeting, as well as the amounts super PAC has disclosed spending in their races (the group hasn't yet reported spending in primaries scheduled for late March, April and May):

Marcy Kaptur, D-Ohio: $253,179

Spencer Bachus, R-Ala.: $156,095

Jean Schmidt. R-Ohio: $49,043

Jo Bonner, R-Ala.: $70,341

Jesse Jackson, Jr.: $43, 057

Don Manzullo, R-Ill.: $600

Judy Biggert, R-Ill.: $0

Tim Holden, D-Pa.: $0

Tim Murphy, R-Pa.: $0

Eddie Bernice Johnson, D-Texas: $0

Silvestre Reyes, D-Texas: $0

The super PAC is focusing on districts that solidly favor one party or another, Ellis said. The group has said it wants to counter-balance incumbents’ fundraising advantages, which CPA contends comes mostly from lobbyist and special interest money.

To University of Akron political science professor David B. Cohen, it seemed odd that an anti-incumbent group entered the fray in Ohio's newly redrawn 9th Congressional District. “Neither Kaptur nor Kucinich are political amateurs–they are longtime members of Congress both capable of raising buckets of money and waging a competitive campaign,” Cohen wrote in an email. Indeed, Kucinich had raised nearly $1 million by mid-February, and had more than a 2-to-1 money advantage over his opponent, Rep. Marcy Kaptur, D-Ohio, according to the Center for Responsive Politics.

Despite that advantage, the CPA backed Kucinich, the liberal firebrand, dispensing more money in that race than any other. Even so, Kucinich lost to the more conservative Kaptur, who benefited from a district drawn more to suit her. Kaptur’s opponent will be none other than “Joe The Plumber,” of 2008 presidential campaign fame. His real name is Samuel Wurzelbacher.

From mid-February through the primary, the CPA spent at least $250,000 on advertisements, phone calls and mailings criticizing Kaptur or boosting Kucinich. But the campaigns themselves turned negative that month too. As of mid-February, Kaptur had spent $230,000 on media and Kucinich had spent $137,000, according to the Center for Responsive Politics.

The founders of CPA and the Alliance for Self-Governance are Leo Linbeck III and Eric O’Keefe. Both are also behind the Health Care Compact, which urges states to band together to ask Congress to take the regulation of health care away from the federal government. Linbeck doesn’t consider himself a conservative, Ellis said. He is “conservative communitarian” and “not a small government type.”

O’Keefe founded a group that advocated for congressional term limits in the 1990s and is on the board of the libertarian Wisconsin Club for Growth and the Center for Competitive Politics, a group seeking to reduce campaign finance regulations.

Linbeck has contributed $775,000 to CPA thus far, O’Keefe $100,000. Another six-figure donor is Joe Ricketts, the founder and former chairman of TD Ameritrade, who resides in Wyoming and whose family owns the Chicago Cubs. Tim Dunn, the CEO of a Texas-based oil and gas well company called Crownquest, is another six figure donor. Donors to the nonprofit Alliance for Self-Governance do not have to be disclosed and the group's IRS tax forms could not be found.